Electromagnet



Dec. 14 1926. 1,610,744

E. R. CARICHOFF ELECTROMAGNET Filed Feb. 18 1922 -nnllmmmllfl f Cgi/4 jla l vl/T\I\/el*ltor'-Z Eugene FQ. carichoff, WM 24. g H15 Attorney.

Patented Dec. 14,v 1926. A

UNITED STATES' l 1,610,744 PATENT OFFICE.

EUGENE R. AQARICHOFF, OF SCHENECTADY, NEW YORK, 'ASSIGNOR T0 GENERALELEC- TRIC COMPANY, A CORPORATION F N 132Wl YORK.

Application filed February .18,41922. Serial No. 537,607.

The present invention is directed to im` the invention has a particularapplication in electromagnetic switches of the series lockout type. In aprior patent issued to Benjamin W. Jones and myself, No. 1,445,994,datedFeb. Q0, 1923, and assigned to the same assignee as thisapplication, there is described an improved form of series lockout vtypevelectromagnetic switch to'which the improvements ofthe presentinvention apply Y'to great advantage, and the principles of thisinvention will therefore be explained in connection with a switch of thetype disclosed in the said Carichof and Jones application. In the saidCarichoi' and Jones application there is disclosed and broadly claimedan electromagnetic switch having a series coil and a movable magneticmemE ber or 4plunger disposed within the series coil so as to form apart of the magnetic circuit of the switch. The plunger is connected toa switch member and is disposed with respect to the magnetic circuit ofthe switch so as to provide two air gaps, one of which is a holdingopen7 air gap and the other is a closing air gap. The arrangement issuch that the plunger will be magnetically held in its biased or openposition by the magnetic pull across the holding open air gap when thecurrent in the series vcoil is above a predetermined value and thelungerY will be operated to and magnetically eld in the closed positionoi the switch by the magnetic pull across the closing gap when thecurrent in the series coil drops to the predetermined value. A shuntcoil is disposed on the magnetic circuit of the switch for insuring thatthe switch will positively close when the currentin the series coil islbelow the predetermined value, and for insuring that the switch willnot automatically reclose after opening when the current through theseriesl coil is reversed..

(Dine ci the objects of my invention `is to prevent the series excitingcoil of the switch electroniagnet from interfering with the movements ofthe movable magnetic member' or plunger.

Another cbiect of my invention is to prevent interiierenec by the seriesexciting coil of the electromagnet with the adjustment of theCalibrating device for adjusting the holding open air gap of theelectromagnet.

Another object is to provide an improved arrangement in which themovable magnetic member of the electromagnet is perfectly free to movewithin the series coil without any wedging action.

A further object is. to provide an im-` proved arrangement lforsupporting the movable magnetic member of the electromagnet when thesaid member is in its biased position.

Another object is to provide an improved arrangement involving the useof a magnetic tube on whichthe series coil is disposed and on which themovable magnetic member is supported in such a manner that dirt and dustis prevented from entering the tube.

A still further object of the invention is .to provide an arrangementwhereby the movable magnetic member or plunger is prevented fromoperating at the calibrated value when the current in increasing quicklypasses through that value. Thus, in case the electromagnet is used in aswitch for controlling -the acceleration of a motor in response to thecurrent taken by the motor, when the motor is first connected to thesupply circuit, there is a rush of current and it is desired that theswitchY shall close when the motor current drops to theipredetermined orcalibrated value and not when the current passes through that valuewhile the value of the current is increasing.

Further objects and purposes of the invention will appear in the courseof. the :tol-

lowing specilication in which I shall disclose' the invention embodiedin concrete form for purposes of illustration.

Referring to the drawings, Fig. l is a side vie-wwf an electromagneticswitchl of the series contactor type, disclosed and broadly claimed inthe said patent of BenjaminW'. Jones and myself, with the improvementsof the present application incorporated therein; F ig. 2 is a front viewof the switch shown in Fig. l; Fig. 3 is 'a cross-section detail of theseries' electromagnet of the switch of Figs. l and 2, with theimprovements of the present invention shown in detail; Fig. 4 is adetail showing a modification of Fig. 3 in the manner of supporting theplunger associated with the series electromagnet; and Fig. 5 is a verysimple diagram ofY connections showing the'series contactor employed inthe control of an electric motor.

Referring to the drawings, and particularly to Fig. 3, the seriesoperating electromagnet of the switch is provided with a series windingwhich is mounted upon a spool 11 of insulating material. This spool andthe winding are mounted upon the tube 12 of magnetic material which isof a substantial rigid construction, so that the winding spool andwinding are securely held with respect to this tube. The plunger 13 hasits major portion disposed within the tube 12, and this plunger has anenlarged 1- head 14 which projects from and is supported by the upperend of the tube 12, so that when the plunger is in its biased position(that shown in the drawing), the plunger will be separated from theupper end ofAthe adjustable plugl of magnetic material so as to providean air gap which is commonly termed the holding open air gap. Theenlarged head 14 of the plunger rests upon a washer or spacer 16 ofnon-magnetic mate- J rial which magnetically separates the plunger fromthe tube to prevent the p unger i from sticking tothe tube and provideswhat amounts to an air gap whereby the* plunger will not operate whenthe current increasing through the series coil-passes quickly throughthe operating value. The cylinder 17 of non-magentic material such asbrass or the like, is disposed within the tube 12 so as to prevent theplunger 13 from sticking to the side walls of the tube 12, and also toserve as a shading coil for the flux passing from the tube into theplunger. I have Vfound that it is desirable that the crosssection of theIplunger within the tube shall be about fifty percent greater than thecrosssection of the tube 12, although my invention is not necessarilylimited to thisparticular relation between the cross-section of the twoparts. The spool 11 is securely held with respect to thetube 12 by meansof the spring washer 18 which is suitably interlocked with theupperendof the tube 12 as shown. With the adjustable plug 15 mounted inthe lower end of the tube 12, this tube is closed at its lower end, andthis lower end of the tube is secured in a frame 19 of magnetic materialwhich extends upward and over the projecting head of the plunger so asto form an air gap between the upper surface of the enlarged head of theplunger and the magnet frame. This air gap which is designated by thenumeral 2O is termed the closing air gap.

Instead of supporting the plunger within the tube 12 as shown in Fig. 3,this plunger may be supported in other ways, as for example, by a smallcylinder of insulating material 21 as shown in Fig. 4.

Referring now to Figs.l 1 and 2, the enlarged or upper end of theplunger 13 is piv- -motor armature to the source otally connected to onearm of the bell crank of current below the calibrated'valuemthat .i

value at which the switch is no longer magnetically held in the openposition--,` and also for insuring that the switch will not recloseafter opening in response to a reversal of current through the seriescoil 10.

The magnetic blowout which is disposed adjacent the switch contacts 22and 23 comprises plates of magnetic material 25 and 26 between which theare chute 27 of refractory material is supported. The plates 25 and 26are respectively connected by means of the strips 28 and 29 of magneticmaterial so as to be across the closing gap 20. A. very simple magneticblowout -is thereby provided, and this magnetic blowout is dis closedand claimed in a .prior patent of mine No. 1,503,091, dated July 29,1924, and assigned to the same assignee as this invention. The variousparts of the switch aremounted upon a suitable base 30 of insulatingmaterial. t

As thus constructed Aand arranged, and with the parts in theirrespective positions as shown in the drawings, the operation of theswitch may be described in connection with Fig. In order to connect themotor having an armature 31 and a shunt field 32 to the supply circuit33, the disconnecting switch 34 is first closed, thereby energizing theshunt field 32 of the motor directly across the supply circuit. In orderto connect the pilot lswitch 35 will be closed, thereby energizing theline contacter 36 to close and 'thus connecting the motor armature tothe source of supply with the accelerating resistor 3T included incircuit therewith. The series coil 10 of the switch described inconnection with Figs. 1, 2, 3 and 4 is included in series with thearn'iature of the motor and the shunt coil 24 is connected across thesource of supply bythe closing of the lauxiliary switch 38 associatedwith the line contactor 36. The plunger 13 will be magnetically held bythe pull across the holding open gap between the lower end of theplunger and the upper lend of the adjustable plug 15 as long as thecurrent through the motor armature is in excess of the predeterminedvalue.

It will be lobserved that when the'motor armature circuit isestablished, the current through the series coil 10 quickly rises fromthe zero value through the predetermined lllfi lll) lil]

operating or calibrated value to a value at (which the switch ismagnetically locked open. The arrangement in accordance with` myinvention will prevent the plunger from operating when the currentpasses quickly through the calibrating value as the current increases,and While I do not limit myself to any particular theory of operation, Ibelieve the explanation of this desirablefeature of ,the invention to beas follows: As previously pointed out, the spacci" 16 provides Whatamounts to an air gap between the upper edge of the tube 12 and thelower surface of the enlarged head 14 of the-plunger. The path for themagnetic flux from the tube 12 to the plunger/is damped by the cylinder17 so that an appreciable flux passes across this air gap from the upperedge of the tube to the head of the plunger, thus producing a magneticholding down effect which prevents the plunger temporarily from rising,`As soon as the rate of change of the current bccomes substantiallyconstant, the damping effeetof the cylinder 17 ceases and the mayorportion of the flux passes directly into the lower portion of theplunger. When the current drops to the predetermined value, the pullacross the closing gap 20 will predominate and the plunger 13 Willbemag-. netically raised into operative engagement With the magnet frame19, thereby closing the air gap 20. This will cause the switch contact22 to make engagement withthe stationary contact 23 and thereby shortcircuit the accelerating resistor 37. After the switch is thus closed,it will be magnetically held closed by reason of the magnetic yeffectupon the plunger 13.

It Will be observed by reference to Fig; 3 particularly, that the seriesexciting coil pf the switch electromagnet isprevented from interferingwith the movements of the movable magnetic member or plunger 13, be-

{cause of the fact that this coil is rigidly f mounted in position andcannot be distorted from its normal position so as to interfere with themovementsof the plunger. Y The series exciting coil of the electromagnetis prevented from being displacedv and thus interfering With theadjustment of the plug 15 to thereby regulate the value of currentthrough the series coil 10 at which the switch will magnetically closeand be held closed. Furthermore, the plunger is supported in its rbiased position in a very neat, simple and effective manner, and withthe parts prop erly fitted, no Wedging action of the plunger isnecessary. The series operating electromagnetl is simple in constructionand of such a form that rit lends itself readily to large scalemanufacture, as will be readily understood by those skilled in the art.It will also be observed that by reason of the cylinder 17 and the airgap between the upper edge of.

the tube l2 and the head 14.- of the plunger,

the plunger is prevented from operating when the value ofcurrent'through the coil 1() rises quickly through the predetermined orCalibrating value. I

In accordance with the provisions of the patent statutes, I havedescribed the prin ciple of operation of my invention, together with theapparatus which I now consider to yrepresent the best embodimentthereof, but I desire to have it understood that the ap: paratus shownis only illustrative and that the invention may be carried out by othermeans.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. An electromagnet comprising atube of magnetic material closed at oneend, an eX- citing coil surrounding the tube, `a plunger biased to oneposition and disposed in the tube for reciprocation therein under thecontrol of said coil, one end of said plunger projecting from the tubeand the other end ofthe plunger separated from the closed end of thetube by a holding air gap across which the flux of'said coil passes tohold the plunger in the biased position, means disposed in the closedend of the tube for adjusting the said holding air gap, and a frameof-magnetic material attached to the closed end of the tube andextending over the projecting end of the plunger to provide a closingair ap between the said rojecting end ofthe p unger and the said flf'amewhich is normally open and is closed by the operation of said plungerwhen the magneticV pull across the same is greater than the magneticpull across the said holding air gap.

2. An electromagnet comprising a tube of magnetic material, an excitingcoil surroundin the tube, a plunger having a major ortion isposed withinthe tube and an enarged head supported by the tube with an air gapinterposed between said head and the supporting end of the tubefa plugof magnetic material closing the other end of said tube and providing anadjustable air4 gap between the plug and the end of the plunger withinthe said tube, and ay frame lof magnetic material secured to the closedend of said tube and extending over the said enlarged head of theplunger and separated from said head by an air gap.

3. An electromagnetcompri-sing a tube of magnetic material, a spoolhaving a coil supported thereonv disposed over the tube, a-

spring Washer interlocked with the tube for holding the spool withrespect to the tube,

a plunger having the major portion thereof disposed withinthe tube andan enlarged head rojecting from and supported by one end o the tube, anadjustable plug of magnetic material closing the other end of the tubeand extending toward but separated from the end ofqthe plunger withinthe tube by an air gap, and a frame of Ymagnetic ing the tube,` aplunger having the major material attached to the'closed end' ofthe tubeand extending over the projecting end et the plunger.

4;. An electromagnet comprising a tube ot magnetic material, an excitingcoil surroundportion thereofJ disposed in the tube and an enlargedheadprojecting from the end of the tube, a spacerof non-ma netic'material betWeentlre-said enlarged hea of the plunger and the one endof'said tube providing one air gap in the magnetic circuit oftheelectromagnet,` a non-magnetic cylinder disposed over the said majorportion of the plunger,

` and an adjustable member of magnetic maand tube for holding the spoolin position on the tube, a lunger having theJ ma or portion thereofdisposed in the vtube an an enlarged head projecting from the end ofthetube, a spacer of non-magnetic material be e l tween the said enlargedhead of the plunger and the said end of the tube, a nonmagnetic metalliccylinder disposed over the said major portion of the plunger, anadjustable plug o1c magnetic material closing the other end of the tubeand extending toward but separated from the end of the plunger Withinthe tube to provide a holding air a and a frame of magnetic materialattahdtl to the closed end 4of the tube and extending over theprojecting end of the plunger 'to provide a closing air gap which isnormally yopen and is closed when the magnetic pull across the same isgreater than the pull across said holding air gap.

In Witness whereof, I have hereunto set my hand this 17th day ofFebruary, 1922. EUGENE R. CARICHOFF.

